1. Field of the Invention
The present invention relates to a communication apparatus that performs wireless communication.
2. Description of the Related Art
If a mismatch (difference) exists between impedance of an antenna used in wireless communication and impedance of a transmission unit connected to the antenna, when the transmission unit supplies a data signal to the antenna, the antenna reflects a wave. The larger the impedance mismatching, the larger the intensity (reflected power) of the reflected wave and the smaller the intensity of the radio wave emitted from the antenna. In view of this, Japanese Patent Application Laid-Open No. 7-7357 discusses a configuration to reduce intensity of the reflected wave. Based on the configuration, the mismatch between impedance of the antenna and impedance of the transmission unit is minimized based on intensity of the reflected wave.
In relation to antennas, a technique enabling wireless communication by bringing antennas close to each other is widely used. For example, Japanese Patent Application Laid-Open No. 2008-271606 discusses such a technique. Based on a configuration discussed in this application, an antenna of a user apparatus and that of a communication partner are faced with each other so that the pair of opposed antennas operates as a capacitor. These antennas form an induction electric field therebetween to communicate with each other.
As described above, impedance mismatching between an antenna and a transmission unit generates a reflected wave. However, when the antennas are brought close to each other for communication, since the above pair of opposed antennas operates as a capacitor, the impedance between the antennas changes depending on a positional relationship between the user apparatus and the communication antenna. As a result, a reflected wave is generated.